Many people who exercise, such as runners, cyclists or the like, often desire the ability to monitor their workouts for performance and motivation reasons. To meet this need, many personal training devices are available on the market for monitoring and in some cases tracking a run, ride or workout.
One example of personal training devices are step counters (or pedometers), foot-pad sensors (e.g. accelerometers) and tachometers. These devices can monitor and track the distance travelled by a user, e.g. a runner, by counting the number of steps made by runner.
In recent years, the use of GNSS (Global Navigation Satellite Systems) receivers, such as GPS, has started to be used in personal training devices. For example, sports watches that include GPS antennas have started to be used by joggers, runners, cyclists and other athletes and outdoor enthusiast as a means to obtained real-time data of their speed, distance travelled, etc. Unlike the step sensors mentioned above, these GPS devices provide the user with the ability to track and record the route they have travelled, and to subsequently “map” this route for later analysis. For example, the GPS data stored on such devices can be transferred to a computer or website by a user after they have completed their activity so that the route can be displayed on a digital map.
As will be understood by those skilled in the art, the position and speed data obtained from GPS receivers will typically be effected by slowly time-varying errors. Such errors can be reduced to a large extent in vehicle navigation systems, such as conventional portable navigation systems (PNDs), using various filtering techniques such as Kalman filtering and map matching. The different, and generally more complex, dynamical behaviour of pedestrians and other outdoor enthusiasts, however, means that conventional filtering techniques cannot be used, or at least are significantly less effective. Furthermore, many runners, cyclists, etc will carry out their exercise areas where satellite visibility might be impaired, e.g. dense urban environments having numerous tall buildings. Accordingly, when the GPS traces obtained from conventional personal training devices are displayed on a digital map, the route shown may contain numerous inaccuracies, both small and large, when compared to the route actually travelled by the user.
It would therefore be desirable to provide a mobile device that can record data associated with the route travelled by a user in a manner that allows a more accurate route to be displayed on a digital map. Since the data storage capability of such mobile devices is generally rather limited, it would also be desirable to record data relating to the route in an efficient, or compressed, manner.